Previous research has identified individual-level and situation-specific risk factors for sexual risk behaviors among men who have sex with men (MSM), with substance use and depression having a particularly adverse impact. HIV behavioral interventions have shown reductions in sexual risk behaviors among MSM, but there are a limited number of efficacious interventions and most do not address multi-level factors which could affect risk behaviors. Research has shown that neighborhood characteristics influence disease outcomes and health behaviors. Our preliminary data suggest that neighborhood does matter for sexual risk among MSM. Our results lead to further questions as to the specific effects of where men reside (residential neighborhood) and where men spend most of their time socializing (social neighborhood) on sexual risk behaviors, substance use and depression. The purpose of this multi-level, cross sectional study is to identify key neighborhood-level characteristics that may influence sexual risk behaviors, substance use and depression among MSM. The specific aims of this study are to: 1) identify neighborhood characteristics that MSM consider likely to influence their sexual behavior, substance use and depression, using qualitative methods, to inform our measures; 2) characterize neighborhood variation in sexual risk behaviors, substance use and depression among MSM using quantitative methods; 3) characterize the associations between objectively measured neighborhood-level characteristics and risk behaviors, substance use and depression among MSM after accounting for individual level factors; 4) characterize the associations between perceived neighborhood-level characteristics and risk behaviors, substance use and depression among MSM after accounting for individual level factors; and 5) determine the role of individual-level characteristics in shaping perceptions of neighborhood and modifying the influence of neighborhood characteristics on risk behaviors, substance use and depression among MSM. To achieve these aims, we will enroll a geographically and ethnically diverse sample of 1500 MSMs in New York City. Participants will provide information via ACASI on their sexual risk behaviors and substance use and depression, perceptions of residential and social neighborhoods and individual-level covariate data. Using data reported by participants, spatial analytical methods will be used to create surface density maps of neighborhood characteristics. This will be added to information from an existing extensive geospatial database of New York City neighborhood characteristics for a comprehensive picture of relevant urban characteristics. Key hypotheses will be tested using multi-level hierarchical modeling to capture independent neighborhood level effects. The results will add new information to a growing understanding of whether and how the urban environment influences sexual risk behaviors, substance use and depression and may have direct implications for design of structural, community-based and outreach interventions for MSM. PUBLIC HEALTH RELEVANCE: The purpose of this study is to identify key characteristics of neighborhoods and perceptions of neighborhoods within urban environments that may influence sexual risk behaviors, drug and alcohol use and depression among men who have sex with men. This study will have direct implications for the design of structural, community-based and outreach interventions for men who have sex with men.